"I did this while teaching about germs and how they spread," she wrote. "You use three pieces of bread. You let all the kids see you put a piece of bread in a baggy with a glove on hence 'controlled' then you wash your hands and put a piece of bread in a baggy for 'clean' last but definitely not least you pass a piece of bread around and let every kid in class touch it then you put it in a baggy and label it dirty. Watch how the bread changes over time due to germs. It is so cool and a great way to teach the importance of hand-washing."

The results are striking. In the photo Simpson shared, the control slice and the slice of bread that was touched with clean hands look completely edible. However, the bread that was touched with "dirty hands" is almost entirely covered in mold. Simpson didn't specify how much time had passed since handling the bread and putting them in bags, but does it really matter? You can't look at this photo without wanting to wash your hands.

The post has since been shared over 300,000 times and has over 180,000 likes. Many teachers have thanked Simpson for sharing the experiment with them and commented that they plan to use it as well.